RAM Connection HSS Weld Question

When RAM Connection computes the effective weld length of an HSS T-connection, it correctly applies this rule per AISC 360-16: 

When β > 0.85 or θ > 50°, Be / 2 shall not exceed Bb / 4.

However, when computing the effective section modulus of the same connection for in-plane and out-of-plane moments it does not limit Be/2 to Bb/4.

The way I read the code this is not correct. Am I missing some obscure note in the code that allows this or is this an error?

Here’s a sample calc from RC showing what I’m talking about. I did not include the out-of-plane bending calc but it used the same effective width as the in-plane.       

Weld calculation for brace member with axial load

 

        Weld strength                                                                 [Kip]                  222.74             118.00    DL                0.53    Eq. K5-5

            b = Bb/B

            = 8[in]/8[in]

            = 1                                                                                                                                                                              

 

            Be = Min((10*t/B)*(Fy*t)/(Fyb*tb)*Bb, Bb)

            = Min((10*0.625[in]/8[in])*(50000[lb/in2]*0.625[in])/(50000[lb/in2]*0.5[in])*8[in], 8[in])

            = 7.81[in]                                                                                                                                                                    Eq. K1-1

 

            (b>0.85) or (q>50) ® (1>0.85) or (90>50) ® True                                                                                                 

 

            Bew = Min(Bb/2, Be)

            = Min(8[in]/2, 7.81[in])

            = 4[in]                                                                                                                                                                         Eq. K5-5

 

            le = 2*Hb/SinDeg(q) + 2*Be

            = 2*8[in]/SinDeg(90) + 2*4[in]

            = 24[in]                                                                                                                                                                       Eq. K5-5

 

Weld calculation for brace member with in-plane bending

        Weld strength                                          [Kip*ft]             64.84                  15.00                   DL    0.23                  Eq. K5-6, K5-2

            Be = Min((10*t/B)*(Fy*t)/(Fyb*tb)*Bb, Bb)

            = Min((10*0.625[in]/8[in])*(50000[lb/in2]*0.625[in])/(50000[lb/in2]*0.5[in])*8[in], 8[in])

            = 7.81[in]                                                                                                                                                                    Eq. K1-1

 

            ApplyCondition = (Pro/3)*(Fyb/SinDeg((1/W)))2 + Pro*Be*(Fyb/SinDeg((1/W)))

            = (0.442[in]/3)*(8[in]/sin(90))2 + 0.442[in]*7.81[in]*(8[in]/sin(90))

                = 37.05[in3]

  • Hello, you are correct. We are following the rules of AISC 360 Table K5.1 to limit the value of effective width for weld strength calculation for T, Y or X truss connection type, but we are missing this limitation for the effective elastic section modulus of the welds for both in-plane and out-of-plane bending. We will fix this for next release. Please, if you need a RAM Connection build contact us via TS or click here.

    Answer Verified By: Tank 

  • Thanks, Carlos. As you reduce the effective section modulus there will be cases where the welds are quite large. AISC 360-16 says the following in section K5, "The weld checks in Table K5.1 are not required if the welds are capable of developing the full strength of the branch member wall along its entire perimeter (or a plate along its entire length)." Do you have plans to incorporate this by calculating this and using it instead if the size is smaller than the "fit for purpose" size?